Chapter 24: Human Origins and Evolution

Question 1

define primates. what characteristics do they have that make them different from other mammals?

Answer 1

-"prosimians" = (lemurs, bushbabies) 
monkey's + apes
-nails rather than claws
-eyes in front instead of on the side (allowing 3 dimensional vision)
-opposable thumbs

Question 2

from which three pools of information do we gather our information to trace lineage of organisms?

Answer 2

-The fossil record
• The DNA (molecules)
• The physical features (anatomy)

Question 3

what are included in the “great apes”?

Answer 3

orangutan 
gorilla 
chimpanzee
humans 
(we are all part of the same monophyletic group because we are all descendants of a common ancestor)

Question 4

which member of the “great apes” are the sister group to humans? (closest related)

Answer 4

chimpanzees

we differ in DNA sequence by just 1%!

Question 5

what is Sahelanthropus tchadensis?

Answer 5

the earliest hominin

• blend of human and chimpanzee skulls
• 7 million years ago was when the split began

Question 6

what is Australopithecus afarensis?

Answer 6

“Lucy”!

• 3.2 million years ago
• bipedal
• less than 4 feet tall

Question 7

what is Ardipithecus ramidus?

Answer 7

“Ardi”

• 4.4 million years old
• bipedal on land, quadrupedal in trees

Question 8

when did hominins go completely bipedal?

Answer 8

somewhere between Lucy and Ardi

Question 9

“sapiens”

Answer 9

modern

Question 10

“neanderthanensis”

Answer 10

from Neandertaler

Question 11

“floresiensis”

Answer 11

from Indonesian island of Flores (known as the “hobbit”)

-adults just over 3 feet tall

Question 12

“erectus”

Answer 12

upright

Question 13

“heidelbergensis”

Answer 13

from heidelberg

Question 14

“ergaster”

Answer 14

working

Question 15

“rudolfensis”

Answer 15

from Lake Rudolph

Question 16

“habilis”

Answer 16

nimble, quick, swift

Question 17

how many mya did the hominin lineage first wander out of africa?

Answer 17

about 2 million years ago

Question 18

homo eragaster/homo erectus

Answer 18

first hominin to venture out of africa

Question 19

when did Neanderthals first appear?

Answer 19

• first appeared in fossil record about 600,000 years ago

- disappeared about 30,000 years ago

Question 20

why do mammals often evolve small body size on islands?

Answer 20

because limited availability of food

Question 21

what is the “multiregional hypothesis” of human origins?

Answer 21

• Homo ergaster roots
• Migrated out of Africa about 2 mya
• Many separate migrations from different populations
• Modern humans evolved in parallel out of these
different pop’ns.
• Proven incorrect by the Out of Africa theory

Question 22

what is the “out of africa” hypothesis of human evolution?

Answer 22

• Much more recent move from Africa
• 200,000 ya rather than 2 mya
• Modern humans evolved from H. ergaster (H.
heidelbergensis) while still in Africa
• Then split off to various pop’ns as they continued to
migrate and separate across the region

Question 23

mitochondrial DNA (mtDNA)

Answer 23

• small circle of DNA about 17,000 base pairs long
• found in every mitochondrion
• much more abundant than nuclear DNA and easier to extract
• no recombination in mtDNA
• all mtDNA is inherited by the mother (allows us to trace mutations because thats the only way genetic changes could arise in this form of DNA)

Question 24

what is some evidence for/against humans ad neanderthals interbreeding?

Answer 24

1. Neanderthal and Modern
   did interbreed but the
   mtDNA has since been lost.

2. Neanderthal males
interbred with Modern
females but Neanderthal
females did not interbreed
with Modern males.

3. 600,000 year difference, at
   least

Question 25

define neoteny

Answer 25

when a sexually mature organisms still retains juvenile physical characteristics

Question 26

what are 4 anatomical factors that must have changed to make the shift from quadrupedal to bipedal possible?

Answer 26

1. foramen magnum (hole in base of skull) repositioned so that human skull is balanced directly on the vertebral column
2. spine - S -shaped to ensure weight is directly over the pelvis
3. legs - legs directly under body, stronger to support weight
4. feet - human foot is narrower and has a bigger arch with a larger big toe

Question 27

what are some selective factors that allowed us to evolve brains which are proportionally too large for our body size?

Answer 27

tool use - manual dexterity, need complex nervous organization

social living - coordination and communication (for example to successfully hunt in groups)

language

Question 28

what are 4 important modern human features?

Answer 28

• Bipedal locomotion
• Neoteny
• Large brains
• FOXP2 gene (plays important role in development and communication)

Question 29

what is the percentage of human genetic variation throughout our species?

Answer 29

• about 1 in every 1000 base pairs is different among humans
• level of human variation is 0.1%
• we are not very genetically diverse!!

Question 30

the human genome consists of approximately how many base pairs?

Answer 30

3 billion

Question 31

about how many years ago did modern humans cross from Siberia to North america to populate the new world?

Answer 31

15,000 years ago